The scope of the invention relates to the elimination of slurry or some other pasty wastes such as fatty wastes, especially slurry from industrial processes or drinking water or used water filtering stations.
More precisely, the invention concerns a system for injecting slurry to be incinerated into an incineration furnace, together with a procedure and a corresponding furnace. The invention will have particular application in dual application furnaces for household waste (or other urban or industrial waste) and slurry and/or fatty wastes. It may be applied to furnaces with different types of combustion (for example, with a fixed or removable incineration hearth, with grids, rollers, fluid bed, etc . . .).
The slurry, in particular slurry which has come from dehydration plants at used water treatment stations, generally has a high content of organic material which is not easily biodegradable. It therefore poses environmental problems and should therefore be eliminated. Furthermore, due to the increasing number of water filtering plants, there is more and more slurry to be treated.
An initial, and already known solution to the elimination is to store same in a dump. However this solution, widely used in the past, is not ecologically acceptable and tends therefore not to be used.
A second, already known solution, including the reusing of this slurry for agricultural purposes would be an ideal solution. Unfortunately, the high costs of storage, transport, spreading and the very nature of the slurry often constitute major obstacles to the implementation of such a solution.
Finally, the third and last already known solution for eliminating slurry is incineration, which produces purely mineral waste. This solution would seem to be the one which is experiencing the most development at the moment. However, when such incineration is used on the filtering station site, using a specific furnace, it may be very costly. That is why when there is already an incinerator in close proximity to the filtering station, for example an incinerator originally intended for another use such as incinerating household waste, it may be economically viable to burn the slurry from the filtering station in the existing incinerator.
Despite the fact that this principle of incinerating household slurry mixed with other products to be incinerated--such as household waste--is already known, implementation of it however, poses several problems.
Thus, according to prior art, the injection of slurry into the combustion chamber of a household waste incineration furnace is generally carried out continuously, in the form of a slurry cylinder.
At the moment, when using this type of injection, the slurry does not disperse in the combustion chamber during injection and so combustion of it is not at its optimum. In other words, the content in the non-burned material of clinker and loose cinders resulting from incinerating the mixture of household waste/slurry may exceed the maximum values imposed in legislation (for example, a maximum of 5% of non-burned material in the clinker).
Additionally, the slurry is not evenly distributed throughout the household waste. There are therefore phenomena of under cooling or over heating in the combustion chamber, depending on whether the incinerated mixture contains a large or small quantity of slurry. These phenomena may disturb operation of the furnace, even cause combustion to stop.
Finally, the variable quality of the slurry to be incinerated, particularly as a function of the dry material which they contain and their calorific value, may also cause phenomena of over heating or under cooling which may cause the boiler to cut off.